Policy
Always expand groups in Office when restricting permission for documents
This policy setting controls whether group names automatically expand to display all the members of the group when selected in the Permissions dialog box. If you enable this policy setting, when users select a group name while applying Information Rights Management (IRM) permissions to Excel workbooks, InfoPath templates, Outlook e-mail messages, PowerPoint presentations, or Word documents in the Permissions dialog box, it will automatically expand to display all the members of the group. If you disable or do not configure this policy setting, when users select a group name in the Permissions dialog box, the members of the group are not displayed.
99358922a0c1L_AlwaysexpandgroupsinOfficewhenrestrictingpermissionfordocumeRegistry
Copy registry mappings
HKCU\software\policies\microsoft\office\16.0\common\drm\autoexpanddls\autoexpanddlsenable (enabled) = 1
HKCU\software\policies\microsoft\office\16.0\common\drm\autoexpanddls\autoexpanddlsenable (disabled) = 0Policy notes
This policy setting controls whether group names automatically expand to display all the members of the group when selected in the Permissions dialog box. If you enable this policy setting, when users select a group name while applying Information Rights Management (IRM) permissions to Excel workbooks, InfoPath templates, Outlook e-mail messages, PowerPoint presentations, or Word documents in the Permissions dialog box, it will automatically expand to display all the members of the group. If you disable or do not configure this policy setting, when users select a group name in the Permissions dialog box, the members of the group are not displayed.